a sanford police detective wrote in his report, i asked mr. martin if the voice calling for help was that of his son. mr. martin, clearly emotionally impacted by the recording, quietly responded, no. george zimmerman's defense attorney, mark o'mara. >> i think cha tracy martin said wasp that's not my son's voice and i think that's information the jury needs to have. >> reporter: in court, the jury has listened to that tape repeatedly, as has tracy martin. whose voice is that? >> trayvon. >> reporter: trayvon martin's parents have not commented during the trial but did an extensive interview with nbc news a month before the trial began. >> i never said, no, that's not trayvon. but after going back to the mayor's office and having a chance to listen to the tape for at least -- i don't know how long. we just played it over and over and over again. i knew then that that was my son. >> reporter: in court, trayvon martin's mother and george zimmerman's mother came to different conclusions. >> ma'am, that screaming or yelling, you recognize that? >>